1. Field of Invention
This invention describes a process to prepare elastic polyurethane flexible foams usable in a cold-molding technique to produce molded articles with good mechanical properties. In particular the invention discloses a process to produce polyurethane molded articles with the lowest possible density and with the highest possible level of mechanical properties as manifested by high elongation, tensile strength, tear strength, and compression under load.
Elastic polyurethane flexible foam articles can be produced in open or closed molds. When molded articles are produced in closed molds, hot or cold foaming techniques can be used with polyether polyols, organic polyisocyanates and various reactants.
Polyurethane foam systems usable in hot and cold molds differ from one another, not only in the starting materials and process techniques, but also in their mechanical properties. Hot foam systems offer advantages in compression/density ratios and in elongation properties of the resultant foam. In a cold foam system the components react fully in a short time without the need for a reheating process, so that comparatively short mold resident times are possible in production of the molded article.
2. Description of Prior Art
The preparation of flexible polyurethane foams from organic polyisocyanates, polyols, blowing agents, catalysts, optionally chain extenders or crosslinking agents, auxiliaries and additives is known in numerous patents and other publications. We might refer, for example, to the monographs by J. H. Saunders and K. C. Frisch, Polyurethanes, Vol. 16 of High Polymers, PTS. 1 and 2 (New York: Interscience Publishers) and R. Vieweg and A. Hochtlen, Polyurethane, Vol. 7 of Kunststoff-Handbuch (Munchen 1966: Carl Hanser Verlag, 1966).
Flexible e-astic polyurethane foam articles--their production, processing techniques, and properties--are described, for example, in Polyurethane, vol. 7 of Kunststoff-Handbuch, ed. Dr. J. Oertel (Munchen, Vienna: Carl Hanser Verlag, 1983) : 212 ff.